RenderletDefinition, type priority and graphs

[Reto Bachmann-Gmuer <re...@trialox.org>]

Summarizing a discussion I just had with Manuel:

- There should be one type priority list for both TypeHandlers and
RenderletDefinitions
- This list should be generated taking into account information from various
sources
- The maximum authority on type ranking should be the system graph
- Only built-in RenderletDefinition should be in the config-graph so that
moving the content-graph from one instance to another (with the same set of
bundles) results in the same site
- Both configuration graph and content graph may contain type ranking hints
- RenderletDefinition added via renderlet-manager go to the content graph

Reto